The present invention relates to file management technology for efficiently using a file system that is configured from storage volumes of different performances and prices.
Various types of recording media are used in a computer system. For instance, a hard disk device a computer system may be a SATA (Serial AT Attached) drive, a SAS (Serial Attached SCSI) drive, a FC (Fibre Channel) drive or the like.
A SAS drive and an FC drive have an expensive unit price per capacity in comparison to a SATA drive, but are able to process the writing and reading of data at high speed. In recent years, an SSD (Solid State Disk) is being used as a recording media that is faster and more expensive than a hard disk device. These expensive high-speed recording media are suitable in storing data that is updated frequently.
Meanwhile, an inexpensive low-speed drive is suitable for storing data that is hardly updated.
Generally speaking, it is said that the amount of data that is updated frequently is roughly 20% of the total data amount, and storage costs can be reduced by properly using the recording media to be used in accordance with the update frequency of data. As a result of taking note of this fact, known is a hierarchy file management system that automatically migrates files to a suitable drive based on the update frequency (Japanese Patent Laid-Open Publication No. 2004-295457).